This invention relates to a network system, in particular to a communication node included in such network system.
A communication network system is composed of a plurality of nodes and links connecting these nodes. Typically, the node includes, for example, an electronic exchanger EX or a router. Moreover, the node includes a cross connect. With a recent increase in data traffic, an optical cross connect handling optical signals has been developed. FIG. 1 shows a typical structure of a communication network system using the optical cross connect.
In FIG. 1, a network in which a plurality of nodes, node A to node D, is cross-connected by optical fibers is shown. In each of the nodes, an electronic exchanger EX is connected with an optical cross connect OXC. Each of the electronic exchangers EX accommodates a plurality of user terminals.
The electronic exchanger EX comprises a switch SW and a switch controller. The electronic exchanger EX changes a data input from the user terminal and outputs it to the optical cross connect OXC. At this time, if the plurality of terminals are outputting data to a single node, the data from the plurality of terminals are time division multiplexed to one electric signal to be output to an input port of the optical cross connect OXC.
The optical cross connect OXC functions to output the signal input from the electronic exchanger EX to the network, and to lead the signal transferring in the network to be output to the electronic exchanger EX. The optical cross connect OXC functions to input the signal transferring in the network and send the signal to adjacent another optical cross connect.
As a result, there is provided between each of the adjacent or not adjacent two nodes, an optical signal connection. The optical signal connection will be referred to as an optical path, in the following. There is provided an optical path between the node A and the node B and another optical path between the node A and the node C, in FIG. 1. Furthermore, there is provided another optical path between a node, not shown in the drawings, and the node D. In an optical path allocated between the node A and the node D, plural user data from the node A, or more upstream node, to the node D, or more down stream node, is flowed.
In the network system shown in FIG. 1, each of the optical cross connects OXC transfers a plurality of optical signals in a single optical fiber using optical wavelength division multiplexing techniques. The optical signals are multiplexed by an optical MUX/DEMUX and an optical space-division switch OSW to be transferred in FIG. 1.
Each of the optical cross connects OXC comprises an interface IF, an optical MUX/DEMUX OMD and an optical space-division switch OSW. The data signal transferred from the electronic exchanger EX to the optical cross connect OXC is converted to an optical signal within the interface IF. The generated optical signal is provided to the optical space-division switch OSW. The optical space-division switch OSW inputs the provided optical signal to the output optical fiber directing to a desired optical cross connect.
The operation of the network system will be explained in the following. When starting the communication, each of the terminals designates a terminal to which the data is to be transferred to the electronic exchanger EX. Each of the terminals, at the same time, reports a bandwidth necessary to communicate, to the electronic exchanger EX.
In response to a call from a first terminal, the electronic exchanger EX specifies a second terminal to which the data is to be transferred. The electronic exchanger EX then judges whether the bandwidth reported by the first terminal can be provided between the first terminal and the second terminal, or not. When the electronic exchanger EX judges that the bandwidth can be provided, the electronic exchanger EX receives the call from the first terminal and starts the call process. This means that the electronic exchanger EX watches the capacity of the bandwidth of the optical path between one node and another node. Each of the electronic exchanger EX transfers the data of the call from the terminal to the network management center NMC.
As for a STM (synchronous transport module) service such as conventional telephones and N-ISDN (narrow-band integrated services digital network), bandwidth necessary for the communication is constant and bit rate is not higher than, for example, 64 kbps/channel. Therefore, by reporting the bandwidth necessary for communication before starting the communication, the reported bandwidth can be assured.
Recently however, services with which bandwidth to be used are not assured such as an available bit rate service by an ATM exchanger and an internet protocol communication service by an IP packet exchanger have been started. This means that users do not need to report or reserve bandwidth necessary for the communication to the network in these services. Furthermore, traffic drastically varies in comparison with a conventional communication.
Therefore, it is desired in these services to dynamically establish, without previously fixing, optimum optical paths in accordance with the variation of the communication bandwidth. A number of optical paths should be allocated between nodes in which heavy traffic exists.
Accordingly, it is an object of the present invention to provide a network system capable of dynamically establishing an optimum optical path in accordance with the variation of the communication bandwidth to achieve a maximum throughput.
It is another object of the present invention to provide a communication node adaptable for a network system capable of establishing an optimum optical path in accordance with the variation of the communication bandwidth.
According to the first aspect of the present invention, the network system comprises a plurality of nodes and a network management system. The nodes, and each of the nodes and the network management system are connected through optical transferring paths. Each of the nodes located in the network system comprises an optical cross connect and a packet switch. Each of the nodes accommodates a plurality of terminals.
In each of the nodes, the optical cross connect establishes an optical path through which data signal from its own node to another node is transferred and/or an optical path through which data signal from a node other than its own node to another node is transferred. Each of the nodes monitors the traffic transferring within the packet switch of its own node.
The network management system detects the variation of the communication bandwidth based on the packet flow monitored by each of the nodes. The network management system then establishes an optical path between each of the nodes to optimize the throughput of the network, based on the variation of the communication bandwidth.
According to the second aspect of the present invention, the network system comprises a plurality of nodes and a network management system. The nodes, and each of the nodes and the network management system are connected through optical transferring paths. Each of the nodes located in the network system comprises an optical cross connect and a packet switch. Each of the nodes accommodates a plurality of terminals.
Each of the nodes monitors the start and the end of an application of each of the terminals included in its own node. Each of the nodes reports the start and end of the application to the network management system.
The network management system detects the variation of the communication bandwidth based on the status of the start and the end of the application program of each of the terminals. The network management system then establishes an optical path between each of the nodes to optimize the throughput of the net based on the variation of the communication bandwidth.
According to the third aspect of the present invention, the, network system comprises a plurality of nodes and a network management system. The nodes, and each of the nodes are connected through optical transferring paths. Each of the nodes located in the network system comprises an optical cross connect and a packet switch. Each of the nodes comprises a plurality of terminals.
Each of the nodes marks a time stamp to each management packet to transfer to other nodes. Each of the nodes measures a delay time based on the time stamp when the management packet marked with the time stamp is returned from other nodes.
The network management system establishes an optical path between each of the nodes to optimize the throughput of the network system based on the delay time between each of the nodes.